High temperature gas turbine blades normally have an airfoil shaped body. The body has a main portion with a trailing end forming the downstream portion of the airfoil. Air cooling is used since these blades operate near their maximum allowable temperature. This air cooling may involve internal flow convection cooling, or passing air through openings in the blade forming a film cooling on the outside.
A thick trailing edge produces an aerodynamic loss. Therefore it is preferable to use a thin edge at the trailing edge. It is difficult to provide cooling air holes in such a thin structure and it is therefore known to locate air egress holes near the trailing end. These are located on the pressure side providing film cooling of the trailing end. Air passes through the openings to a cutback portion on the pressure side, so that the extreme trailing edge is substantially only the thickness of the suction side wall. This minimum thickness is limited by fabrication problems and strength requirements.
So called "fat tip" blades have evolved because of a desire to locate abrasive particles on the tip of the blade. The normal thin trailing edge provides insufficient surface for the particles. Aerodynamic efficiency is sacrificed only in the 25% or so portion of the blade near the tip. The remainder of the blade has still the thin trailing edge. The extent of the air opening cutback has been uniform throughout the length of the blade. Over temperature distress has been noted at the trailing edge near the blade tip.